Monday, April 17, 2006

Moving the time delay forward

I measured the voltage and current of H.V. transformer when I changed the time delay. Here is the scope traces when the delay changed from 1280ms to 1580 ms @ 10 kV. Please note the current wave form @ delay less than 1480 ms, there was a current later than the charging current.

There were no miss fire when I set the delay time less than 1480 ms when I increased the high voltage up to 20 kV. After I fix the Prometheus timing, I will try to send the seed beam and adjust the time to synchronize them.

1 comment:

Randy
said...

I am not sure why there is a charging current pulse just near thyratron firing unless it is somehow noise induced. In a system that uses "command" charging such as Prometheus it is always best to fire the system just after the charging cycle is complete. This reduces high voltage stresses on components. The firing time of 1480 ms is a good time but I would have chosen 1380 ms if it were not for the extra charging current spike.

I would normally like to see about 0.1 to 0.2 seconds of "settling time" just before the Thyratrons are fired as in the time delay of 1380 ms. However, I think that we should fire at 1480 ms since we do not know why there is the extra charging spike at the thyratron firing time of 1380 ms. Try not to fire too much at times like that shown for 1580 ms since this could lead to bad conditions for the SCR controller, the Thyratrons during recovery, and resistor heating.

I'm very glad to hear that the system runs well at 20 kV with the timing of 1480 ms. I will send you a Technical Note on some modeling of how to time the Thyratrons for optimum energy transfer to the laser gas. In principle, the rail gap time should be held constant and the X-ray Cathode and Anode optimized for the rail gap time setting. The Thyratrons are then each adjusted to fire (using the current probe that I installed) for optimum energy transfer to the rail gap system and in turn to the laser gas.

Randy

PS -- yes, please send scope traces so I can look at the extra charging current pulses in detail.